The invention generally relates to optical flame detection and particularly to determination of trace elements in liquid fuel flames of combustor systems through thermal atomic emission.
Gas turbines and burners can be configured to operate on different types of fuel including gas and liquid fuels. While gas fuels, such as natural gas and syngas, represent the majority of installations, the ability to operate using distillate or ash-bearing fuels of varying quality is an important enabler for the gas turbine product line. One major operational difficulty with the use of low-grade liquid fuels is the presence of trace-level metal elements in the fuel that can cause adverse effects on turbine materials, such as hot gas path corrosion and barrier coating degradation. These contaminants, if present, may burn and form reactants that disadvantageously coat the inside of the chamber (combustor) walls, in some cases clogging air flows and prohibiting the system from running optimally. Concentrations on the order of even 1 part per million by mass of some metallic elements in liquid fuel are known to be harmful in this regard. Further, fuel quality differs heavily in various parts of the world where combustor systems are located. Accordingly, it is highly desirable to detect and determine which (if any) contaminants may exist in a particular environment.
The usual defense against hot corrosion due to the presence of some of the metal elements, such as vanadium, is the addition of corrosion inhibitors to the fuel. The concentration of corrosion inhibitors is generally adjusted as a function of the level of metal contaminants in the fuel. An overcompensation of corrosive metal elements by inhibitor may result in the formation of additional ash deposits on the turbine components. Therefore, it is desirable to continuously monitor the levels of corrosive metal elements as well as the corrosion inhibitors in the fuel at the point of use.
Although there are some currently known methods and systems to provide impurity or contamination detection in the liquid fuels, disadvantages exist regarding the complexity and cost of multiple detector systems. Accordingly, there remains a need in the art for systems and methods for measurement of impurities that provide accurate measurements in a more efficient manner.